Area Forecast Discussion
Issued by NWS Greer, SC

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000
FXUS62 KGSP 030743
AFDGSP

AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE GREENVILLE-SPARTANBURG SC
343 AM EDT WED JUN 3 2015

.SYNOPSIS...
UPPER LEVEL LOW PRESSURE WILL GRADUALLY DRIFT ACROSS THE
SOUTHEASTERN STATES THROUGH THE REMAINDER OF THE WORK WEEK.
MEANWHILE A WEDGE OF COOL AIR WILL REMAIN ENTRENCHED OVER MOST OF
THE FORECAST AREA THROUGH THURSDAY. THE INTERACTION OF THESE
FEATURES WILL ENHANCE THE LIKELIHOOD OF SHOWERS AND
THUNDERSTORMS...AND KEEP TEMPERATURES A FEW DEGREES BELOW NORMAL.
THE PATTERN WILL SLOWLY TRANSITION TO MORE SEASONABLE WEATHER OVER
THE WEEKEND.

&&

.NEAR TERM /THROUGH TONIGHT/...
AS OF 340 AM...LATEST SFC ANALYSIS INDICATED A STATIONARY FRONT EAST
OF I-85 WITH A FRONTAL WAVE ACROSS THE MIDDLE SAVANNAH RIVER VALLEY.
RADAR IMAGES SHOW SEVERAL LARGE CLUSTERS OF SHRA/TSRA GENERALLY
ALONG AND EAST OF THE SFC BOUNDARY. WEST AND NORTH OF THE
FRONT...LIGHT WINDS HAVE VEERED FROM THE NNE. BASED ON THE SFC
PATTERN AND RECENT OBSERVATIONS...IT APPEARS THAT WEAK CAD HAS
SETTLED OVER PORTIONS OF THE NC FOOTHILLS AND PIEDMONT. BASED ON
LINGERING CAPES OF 100-500 J/KG AND THE APPROACH OF A MID LEVEL VORT
MAX...CONVECTION MAY EXIST THROUGH SUNRISE...SLOWLY TRACKING NE.

TODAY...NEAR TERM MODELS AND RECENT W/V IMAGES INDICATE THAT THE
CLOSED MID LEVEL LOW WILL CONTINUE TO DRIFT EAST THROUGH THE
DAYLIGHT HOURS. THE 0Z GFS INDICATES THAT THE MAJORITY OF THE
FORECAST AREA WILL REMAIN UNDER AN AREA OF Q-VECTOR CONVERGENCE
THROUGH THIS AFTERNOON. BASED ON THE POSITION OF THE SFC FRONT AND
LIGHT NE WINDS ACROSS THE WESTERN CAROLINAS...IT APPEARS THAT THE
GREATEST MOISTURE POOL SHOULD OCCUR OVER NRN GA. FORECAST CAPES
ACROSS NRN GA INDICATE THE POTENTIAL FOR VALUES ABOVE 2500 J/KG.
INSTABILITY WILL DECREASE TO THE NORTH...WITH THE I-40 CORRIDOR
LIKELY NOT EXCEEDING 500 J/KG. THE RANGE IN CAPE VALUES WILL BE
LIMITED SIGNIFICANTLY BY STRATUS...EXPECTED TO BE WIDESPREAD DURING
THE EARLY MORNING...REMAINING ACROSS THE NC FOOTHILLS AND NRN
PIEDMONT THROUGH THE DAY. I WILL FORECAST LIKELY TO HIGH CHC POPS
ACROSS THE CWA TODAY. HOWEVER...THE POTENTIAL FOR SVR TSRA SHOULD
REMAIN LIMITED TO THE UPPER SAVANNAH RIVER VALLEY. WE WILL MENTION
THE POTENTIAL FOR LARGE HAIL AND DAMAGING WINDS IN THE
HWO...HIGHLIGHTING NE GA AND THE WESTERN TIER OF THE UPSTATE OF SC.
HIGH TEMPERATURES ARE FORECAST TO RANGE IN THE 70S.

TONIGHT...THE CENTER OF THE H5 LOW WILL REMAIN OVER THE FORECAST
AREA...BUT SHOULD CONTINUE TO DRIFT EAST. AT THE SFC...A RIDGE OF
HIGH PRESSURE IS EXPECTED TO RIDGE SW ACROSS THE WESTERN CAROLINAS.
LOW LEVEL MOISTURE AND NE WINDS WILL INCREASE ACROSS THE CWA
OVERNIGHT. WEAK INSTABILITY MAY REMAIN OVER THE LAKELANDS...BUT NEAR
ZERO TO THE NORTH. WEAK ISENTROPIC LIFT AROUND 300 K SHOULD SUPPORT
A FEW SHRA OR PATCHES OF DZ TONIGHT...I WILL HIGHLIGHT WITH CHC
POPS. LOW TEMPS MAY RANGE FROM THE U50S ACROSS THE MTNS TO LOW TO
MID 60S EAST.

&&

.SHORT TERM /THURSDAY THROUGH FRIDAY NIGHT/...
AS OF 230 AM WED...MODELS HAVE TRENDED LATER WITH THE EROSION OF THE
WEDGE...WHICH SEEMS REASONABLE. THEY NOW FEATURE MORE INTERACTION OF
THE SLOW MOVING UPPER LOW AND THE WEDGE BOUNDARY. GFS GOES SO FAR AS
TO CLOSE OFF A SFC LOW OFF THE OUTER BANKS FRIDAY MORNING. CONSENSUS
IS TO MAINTAIN EASTERLY FLOW THRU THURSDAY DESPITE THE PARENT HIGH
PRESSURE MOVING OFF THE NORTHEAST COAST. UPSLOPE INTO THE BLUE RIDGE
WILL CONTINUE TO PRODUCE ABOVE CLIMO POPS...PARTICULARLY ALONG THE
RIDGE ITSELF. VORTICITY PROGS SUGGEST THE LOW WILL BE A BIT TOO FAR
EAST TO PROVIDE MUCH EXTRA LIFT ON ITS OWN...BUT SHOULD CONTINUE TO
ENHANCE LAPSE RATES AROUND THE WEDGE BOUNDARY. THUNDER WILL BE
ADVERTISED ON ITS WARM SIDE. MAX TEMPS WILL STAY A COUPLE CATEGORIES
BELOW NORMAL. MINS FRIDAY MRNG WILL BE NEAR NORMAL.

A DEEP NRN STREAM TROUGH MOVING THRU ERN CANADA WILL BRING A COLD
FRONT TO THE GREAT LAKES AND ST LAWRENCE VALLEY EARLY SATURDAY. THE
TROUGH SEEMS TO PHASE WITH THE UPPER LOW OVER OUR REGION AND HELP
SUSTAIN IT. MEANWHILE A SHORTWAVE WILL ROUND THE SHARP SRN PLAINS
RIDGE AND INTO THE OHIO VALLEY. PAST RUNS HAVE SUGGESTED THIS TOO MAY
MERGE WITH THE TROUGH OR AT LEAST MINIMIZE HEIGHT RISES IN ITS WAKE.
LOW LEVEL FLOW CONTINUES TO REFLECT WEAK OFFSHORE LOW
PRESSURE...FAVORING NORTHERLY. WITHOUT GOOD DOWNSLOPING WINDS TO
SCOUR IT...THE WEDGE COULD HANG ON THRU FRIDAY. A SMALL AREA OF HIGH
PRESSURE IS ANALYZED ON NAM/GFS PROGS OVER THE MID-ATLANTIC WITH A
WEDGELIKE MSLP PATTERN. PROFILES ARE LESS UNSTABLE BUT SUFFICIENT FOR
SLIGHTLY ELEVATED POPS COMPARED TO CLIMO. TEMPS SHOULD REBOUND TO A
COUPLE DEGREES BELOW NORMAL FRI AFTN...WITH LOWS A BIT ABOVE NORMAL
SAT MRNG.

A RETURN OF WEAK SHEAR IMPLIES SLOW MOVING STORMS MAY ENHANCE HYDRO
CONCERNS. MOISTURE IS NOT EXCEPTIONALLY HIGH FRI OR SAT BUT PWAT
VALUES ARE HIGHER THAN THEY WERE TUESDAY...WHEN ISOLATED FLOOD ISSUES
SPRANG UP. SO THE SITUATION WILL LIKELY STILL REQUIRE CAREFUL
MONITORING...PARTICULARLY IF THE WEDGE BOUNDARY IS ABLE TO FOCUS
CONVECTION THU AFTN.

&&

.LONG TERM /SATURDAY THROUGH TUESDAY/...
AS OF 300 AM WED...ANOTHER DOME OF CANADIAN HIGH PRESSURE WILL PUSH
SEWD INTO THE NERN CONUS THRU SUNDAY. THE UPPER PATTERN DOES NOT
APPEAR FAVORABLE FOR IT TO LOCK IN AS CAD...BUT EASTERLY FLOW WILL BE
MAINTAINED INTO THE CWFA SAT AND MOST OF SUN. WILL MAINTAIN ABOVE
CLIMO POPS NEAR THE BLUE RIDGE. MAX TEMPS WILL REBOUND TO JUST BELOW
NORMAL. A LOW PRESSURE SYSTEM WILL FOLLOW THE HIGH...THE SFC LOW
MOVING OVER ONTARIO SUNDAY NIGHT. 03/00Z GFS AND 02/12Z EC DIFFER IN
THEIR DEPICTIONS OF THIS SYSTEM...THE LATTER BEING STRONGER AND
FURTHER SOUTH WITH IT. BOTH MODELS EFFECT A RETURN OF SOUTHERLY FLOW
FOR OUR AREA MONDAY...AND ABOVE NORMAL MAX TEMPS...PRIOR TO THE
ARRIVAL OF THE WEAK COLD FRONT FROM THE ONTARIO SYSTEM. A BROAD AND
SOMEWHAT DEEP TROUGH DIGS INTO THE ERN STATES THEREAFTER...WHILE THE
COLD FRONT STALLS JUST SOUTH OF THE CWFA POTENTIALLY PROLONGING
UNSETTLED WEATHER. GFS FEATURES A SECOND...MORE POTENT COLD FRONT AS
THE AXIS OF THIS TROUGH REACHES THE SRN APPALACHIANS TUE NIGHT. THE
EC HAS BEEN DRIER...AND WHILE THE NEW 03/00Z RUN MAINTAINS THE
OVERALL TRENDS OF THE PREVIOUS RUN...IT HAS NOW COME IN WITH LESS
PRECIP EARLY NEXT WEEK. NONETHELESS ON ACCOUNT OF THE PATTERN CHANCE
POPS WILL BE MAINTAINED MON-TUE.

&&

.AVIATION /08Z WEDNESDAY THROUGH SUNDAY/...
AT KCLT...LATEST SFC ANALYSIS INDICATED A STATIONARY FRONT EAST OF
I-85 WITH A FRONTAL WAVE ACROSS THE MIDDLE SAVANNAH RIVER VALLEY.
RADAR IMAGES SHOW SEVERAL LARGE CLUSTERS OF SHRA/TSRA GENERALLY
ALONG AND EAST OF THE SFC BOUNDARY. WEST AND NORTH OF THE
FRONT...LIGHT WINDS HAVE VEERED FROM THE NNE. BASED ON THE SFC
PATTERN AND RECENT OBSERVATIONS...IT APPEARS THAT WEAK CAD HAS
SETTLED OVER PORTIONS OF THE NC FOOTHILLS AND PIEDMONT. MVFR
CEILINGS WILL BEGIN THE 6Z TAF...LOWERING TO IFR BY 9Z. BASED ON THE
LATEST MOS AND NAM FORECAST SOUNDINGS...IFR CLOUDS MAY LINGER INTO
THE LATE MORNING...THEN REMAINING MVFR THROUGH THE REST OF THE DAY.
WINDS WILL REMAIN GENERALLY VARIABLE THROUGH THE MORNING HOURS...I
WILL FAVOR A NNE DIRECTION. IT APPEARS THAT THE APPROACH OF THE
CLOSED H5 LOW THIS AFTERNOON WILL TRIGGER SHRAS AND POSSIBLY A TSRA
THIS AFTERNOON AND EVENING. I WILL INDICATED IN THE TAF -SHRA
THROUGH THIS AFTERNOON...WITH A PROB30 FOR TSRA FROM 21Z TO 1Z.
BASED ON MESOSCALE MODELS...CAD SHOULD SURGE SOUTHWARD AFTER
SUNSET...I WILL TIME THE RETURN OF IFR CEILINGS AT 2Z.

ELSEWHERE...AT 6Z...CONDITIONS ACROSS THE WESTERN CAROLINAS RANGED
FROM VFR TO VLIFR. IT APPEARS THAT CONDITIONS WILL REMAIN UNSETTLED
FOR THE NEXT SEVERAL HOURS...I WILL HIGHLIGHT MVFR TO IFR CONDITIONS
WITH A TEMP FROM 6Z TO 10Z. HOWEVER...BY SUNRISE TERMINALS SHOULD
OBSERVE IFR TO MVFR STRATUS. THE STRATUS SHOULD LINGER UNTIL MID DAY
ACROSS THE UPSTATE AND MTNS...BUT SHOULD REMAIN THROUGH THE DAY FOR
KHKY. I WILL FEATURE -SHRA FOR MOST SITES DURING THE AFTERNOON
HOURS...ALL SITES A PROB30 GROUP FOR LATE THIS AFTERNOON AND EARLY
EVENING FOR -TSRA. AFTER SUNSET...CAD IS EXPECTED TO SURGE SOUTHWARD
AND RESTRICTIVE CEILING WILL BECOME WIDESPREAD.

OUTLOOK...A MID LEVEL LOW WILL LINGER OVER THE AREA THRU AT LEAST
THURSDAY...WITH DEEP MOISTURE. SO NUMEROUS SHOWERS AND THUNDERSTORMS
ARE EXPECTED EACH AFTERNOON AND EVENING. MORNING STRATUS AND FOG
WILL ALSO REMAIN A POSSIBILITY...ESPECIALLY OVER WET GROUND...THRU
AT LEAST FRIDAY.

CONFIDENCE TABLE...

            07-13Z        13-19Z        19-01Z        01-06Z
KCLT       MED   70%     HIGH  83%     MED   77%     HIGH  81%
KGSP       MED   79%     HIGH  81%     MED   79%     HIGH  80%
KAVL       MED   76%     HIGH  86%     HIGH  94%     HIGH 100%
KHKY       HIGH  84%     HIGH  92%     HIGH 100%     MED   75%
KGMU       HIGH  82%     HIGH  82%     HIGH  84%     HIGH  83%
KAND       HIGH  91%     HIGH  91%     HIGH  97%     MED   75%

THE PERCENTAGE REFLECTS THE NUMBER OF GUIDANCE MEMBERS AGREEING
WITH THE SCHEDULED TAF ISSUANCE FLIGHT RULE CATEGORY. COMPLETE HOURLY
EXPERIMENTAL AVIATION FORECAST CONSISTENCY TABLES AND ENSEMBLE FORECASTS
ARE AVAILABLE AT THE FOLLOWING LINK: (MUST BE LOWER CASE)

WWW.WEATHER.GOV/GSP/AVIATION_TABLES

&&

.GSP WATCHES/WARNINGS/ADVISORIES...
GA...NONE.
NC...NONE.
SC...NONE.

&&

$$
SYNOPSIS...WIMBERLEY
NEAR TERM...NED
SHORT TERM...WIMBERLEY
LONG TERM...WIMBERLEY
AVIATION...NED


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